In aircraft, most electronic equipment is supported on an individual tray which, in turn, is supported at its front and back ends on a pair of cross beams which thus forms a shelf for equipment. The over all size of the trays is standard but the trays accomodate various sizes of instruments. An example of this type of racking or shelving is shown in U.S. Pat. No. 4,458,296 to Bryant et al.
In a typical shelf, a number of trays are closely spaced on the cross beams. Beneath the cross beams and directly below the trays are one or more air plenum chambers to supply cooling air to the instruments and to return heated air after it has passed through the instruments. The return plenum chambers of each shelf communicate with a manifold located at the ends of the shelves which in turn is connnected to a vacuum system.
The outer casing of each electronic instrument is provided with air vents at the top and bottom of the sides to permit cooling air to be drawn through the instruments.
Each tray includes an opening, either with or without a plate, over which the instrument is positioned. Some trays have one or more metering ports in the plates through which cooling air passes. A peripheral gasket is secured around the opening in each tray with its upper portion extending above the upper surface of the tray to sealingly engage the bottom of the electronic instrument supported on the tray and to reduce noise and vibration. With this type of construction, air from beneath the instrument is prevented from leaking past the instrument and, as a result, only the cooling air which is drawn into the system passes through the instrument. An example of this type of tray construction is disclosed in U.S. Pat. Nos. 3,771,023, 3,871,937, 4,044,515 to Hollingsead et al.
A problem exists with the seals of this type of construction when electronic equipment boxes are placed on the tray. When the box is slid or moved on to the tray or removed therefrom, often times the gasket material disengages from the tray and/or the metering plate if one is used with the tray. This not only permits the leakage of cooling air but creates an unstable support for the instrument.
Accordingly, it is an object of this invention to provide an avionic tray gasket assembly which will not disengage or become dislodged when electronic equipment boxes are placed on or removed from the trays.